1. Field of the Invention
This invention relates to a process for forming an organic film, and more particularly to a process for forming a dense organic film having a high quality and a high bonding strength and having various physical and chemical properties controlled as desired.
2. Description of the Prior Art
The formation of an organic film on various kinds of substrates has been conventionally carried out utilizing a mechanical method such as a method of applying on a substrate a film prepared by extruding or stretching a thermoplastic material or a thermal method such as a method of baking an organic solution applied on a substrate. Unfortunately, the conventional mechanical and thermal methods are not adapted to form an organic film of several microns or less in thickness which is homogeneous and has a high adhesion strength. In view of the foregoing, there have been recently proposed some methods such as a plasma method, a vacuum deposition method and the like for the formation of such a film. The plasma method is to deposit an organic material on a substrate disposed in a plasma atmosphere formed by carrying out glow discharge in a vapor of an organic monomer having a low pressure, to thereby form an organic film on the substrate.
However, the plasma method has a disadvantage that it is substantially impossible to prevent the inclusion of a gaseous material introduced to form a plasma and/or other impurities into the film during the formation. Also, there is a fear that revaporization of such gas or impurities often occurs. Another disadvantage encountered with the plasma method is that it is difficult or substantially impossible to externally control operational conditions for forming an organic film and more particularly to externally set and vary the conditions as desired. The plasma method has a further disadvantage of causing undesired heating due to impingement of electrons. Thus, the conventional plasma method cannot be used to form an organic film of a high quality with good reproducibility.
The vacuum deposition method has been proposed, for example, to form an organic semiconductor film from acetylene. However, the so-formed semiconductor is easy to peel due to its poor adhesion strength. This method is also directed to the formation of a thin ployethylene film on a substrate, however, the polyethylene film cannot adhere to the substrate because its bonding strength is substantially zero. Thus, the vacuum deposition method has not been put into practical use for the formation of an organic film.